The present invention relates to a movable hard material plaque intended to cooperate with a fixed plaque in the flow control device of a single control mixer valve.
From the U.S. patent application Ser. No. 513,109 of the same Inventor is known a flow control device for a single control mixer valve, comprising: a structure, a fixed hard material plaque, operatively fixed in said structure, having an upper plane surface and provided with at least two openings for the passage of hot and cold water respectively; a movable hard material plaque, having a lower plane surface disposed in sliding contact with said upper plane surface of the fixed plaque in order to regulate the flow of the hot and the cold water respectively; a control head rigidly connected to said movable plaque and having a coupling means for an operating lever; and a guide member mounted in said structure, rotating for a limited angle about an axis perpendicular to said plane contact surfaces of said fixed and movable plaques, and having guide means cooperating with said control head in order to allow said control head to move, relative to said guide member, only along a diametrical direction thereof; the openings of said fixed plaque being contained within a circle having its center at the intersection between said upper plane surface of the fixed plaque and the extension of the rotation axis of said guide member; and in which said movable plaque has its lower plane surface free from openings and recesses, cooperates with said openings of the fixed plaque exclusively by means of at least a portion of its outline, and said portion of the outline of the movable plaque, intended to cooperate with the openings of the fixed plaque, has a basic configuration free from concave curves and from concave angles, and is situated entirely outside a circle having a radius not smaller than the radius of said circle which contains the openings of the fixed plaque, and having its center at that point of the lower plane surface of the movable plaque which, in the position of total closure, is intersected by the extension of the rotation axis of said guide member.
Thanks to such a control device, the design of the mixer valve is made free from the usual limitations which are imposed to the rotation angle of the operating lever of the mixer valve, and it is possible to attain rotation angles very near the theoretical limit of 180.degree., while the regulation may be carried out on a smaller angle, if preferred, by adopting a suitable configuration of the fixed plaque openings.
However, in certain cases it would be desirable to have the possibility of carrying out the regulation on an angle considerably lower than the limit of 180.degree., although being larger than the usually permitted angle, without having to modify the configuration of the fixed plaque with respect to that which allows obtaining the maximum amplitude of the range of regulation.